A titanium rear sub-frame developed for the Lotus Exige S has reduced weight of the structure by 36 percent and improved stiffness by 19 percent. The development was part of a six-month project between LotusEngineering and Caged Laser to investigate the use of titanium as part of a chassis structure. The project follows one from 12 months ago, when an Ariel Atom chassis was fashioned from titanium. Titanium is incredibly strong – it has the highest strength-to-weight ratio of any metal being as strong as steel but only 45 percent of its weight – but is very expensive, flexible and tricky to treat as it’s chemically neutral. An Exige S’s steel rear sub-frame weighs 50kg, and the project targeted a 30 percent weight reduction. The final weight reduction was 18kg – 36 percent – a significant figure in an already light and tightly packaged car. The torsional stiffness of the frame was also increased by 19 percent, reducing vibration and making the car more stable in the process. The corrosion performance of the two sub-frames was comparable, as was the joining process, which is extensively tested with a variety of different adhesives with the titanium. “We’ve shown we can join titanium and achieve durable joints,” said Lotus’s John Sellors, who unveiled the technology alongside Caged Laser’s Phil Squance at the Niche Vehicle Symposium, an event designed to promote the work of niche vehicle makers in the UK.                                         Sellors added that the technology was now being fitted to a prototype, and that it would begin road trials next week. There’s no word on the technology’s application to a production car.

Photograph: Rear sub-frame weighs 36 percent less than a steel alternative.